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PMM2

Reviewed July 2010

What is the official name of the PMM2 gene?

The official name of this gene is “phosphomannomutase 2.”

PMM2 is the gene's official symbol. The PMM2 gene is also known by other names, listed below.

What is the normal function of the PMM2 gene?

The PMM2 gene provides instructions for making an enzyme called phosphomannomutase (PMM). This enzyme is involved in a process called glycosylation, which attaches groups of sugar molecules (oligosaccharides) to proteins. Oligosaccharides are made up of many small sugar molecules that are attached to one another in a long chain. Glycosylation modifies proteins so they can perform a wider variety of functions. In one of the early steps of glycosylation, the PMM enzyme converts a molecule called mannose-6-phosphate to mannose-1-phosphate. Subsequently, mannose-1-phosphate is converted into GDP-mannose, which can transfer its small sugar molecule called mannose to the growing oligosaccharide chain. Once the correct number of small sugar molecules are linked together to form the oligosaccharide, it can be attached to a protein.

How are changes in the PMM2 gene related to health conditions?

More than 100 mutations in the PMM2 gene have been found to cause congenital disorder of glycosylation type Ia (CDG-Ia). These mutations change the structure of the PMM enzyme in different ways; however, all of the mutations appear to result in reduced enzyme activity. Decreased activity of the PMM enzyme leads to a shortage of GDP-mannose within cells. As a result, there is not enough activated mannose to form oligosaccharides. Glycosylation cannot proceed normally because incorrect oligosaccharides are produced. The signs and symptoms in CDG-Ia are likely due to the production of abnormally glycosylated proteins in many organs and tissues.

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